The present invention relates to performance evaluation soil samples and method of their manufacture, and, more particularly, to soil sample preparation using encapsulation technology to encapsulate analytes which are then introduced into a soil matrix for analysis and evaluation by analytical laboratories.
The demand for precise performance evaluation samples containing contaminants, including volatile organic compounds, in soil matrixes has increased greatly in the recent years. However, there is a lack of sample preparation technology which can accurately and easily replicate such contaminated soil matrices. Current technology for the preparation of performance evaluation soil samples containing volatile compounds has been to utilize solvent spiking (U.S. EPA and Private Sector performance evaluation program providers) or vapor fortification methodologies (J. Hewitt, U.S. Army Cold Regions Research and Engineering Laboratory). The common practice by U.S. EPA, as well as Private Sector companies, is to provide the analyst with a dilute solution of the compounds, or analytes, in methanol. The methanolic solutions can then be introduced either directly to the analytical technique (purge and trap or headspace analyses) or placed onto sand (which is used to simulate soil) just prior to instrumental analysis. However, this practice fails to simulate recovery of the analytes of interest from the soil due to lack of prolonged contact with the soil matrix and may even provide the analyst with an opportunity to analyze the spiking solution directly to assure accurate analytical results.
Furthermore, the vapor fortification method, as described above, yields soil samples with target analyte concentrations only in the low (&lt;100) part-per-billion concentrations. These methods cannot be easily customized to increase concentrations and is not amenable to water soluble analytes. The vapor fortification method will only allow soil samples to reach a concentration that will be in equilibrium with the analyte vapors. Water-soluble analytes are not typically as volatile as non-water soluble analytes and thus come to equilibrium at much lower concentrations in the soil. Some of the concentrations for the water-soluble analytes in the final soil matrix may be significantly lower than ideal. Also, volatile target analytes are easily lost through handling or varying absorbtivity of the soil matrix.
To reduce some of the problems detailed above, the target analytes, including volatile analytes, need to be "hidden" from the analyst, provided to the analyst in the soil matrix, protected from the soil environment (biological activity) and provided in a wide range of concentrations which will result in accurate reproducible results.
In view of the foregoing, the general object of this invention is to provide performance evaluation soil samples which would mimic real world soil samples and provide consistent and realistic levels of contaminants within a soil matrix.
Another object of this invention is to provide a method of preparing soil samples using microencapsulation technologies to encapsulate and place contaminants within a soil matrix.
Yet another object of this invention is to provide soil samples containing microencapsulated volatile organic compounds which would facilitate the evaluation of a laboratory's analytical procedure.
Additional objects, advantages and novel features of the invention will become apparent to those skilled in the art upon examination of the following and by practice of the invention.